A force transducer is used to convert a force into electrical signal. Typically, the force being sensed deforms a strain gauge. The strain gauge measures the deformation (strain) as an electrical signal, because the strain changes the effective electrical resistance of the wire. A force transducer may include four strain gauges in a Wheatstone bridge configuration, as shown in FIG. 1. The output of the force transducer may be plugged into an algorithm to calculate the force applied to the transducer. Typical uses include joystick devices, such as those used in military, industrial, and game systems. For example, a joystick may include a knob or other input structure that a user manipulates using his/her thumb or other finger, to provide a force input, such as to move a cursor, robotic arm, etc.
A strain gauge typically comprises a small resistor that is attached to the object, conventionally by epoxy or cyanoacrylate glue. As the object deforms proportionally to the force applied, the gauge follows it and changes its resistance. In order to achieve a balanced bridge, in the typical prior art approaches the four gauges/resistors used are a carefully ‘matched set’ with very similar resistance and temperature properties. Resistors having very nearly identical resistance are located within a lot or other population of candidates and used together as a matched set. Pairing these resistors can be a complicated and costly process.